The present invention relates generally to the field of switching and, more particularly, to the field of optical switching. Still more specifically, the invention is related to optical switching using ferroelectric materials.
Optical processing is an alternative to electronic systems for situations where electronics do not provide sufficient processing speeds. The fastest electronic sytems have maximum data rates of ten gigabits per second. Fast optical devices operating on many signals in parallel offer vast improvements in several areas of interest including sonar and radar surveillance, electronic warface and communications.
Ferroelectric crystals are common elements in optical processing sytems. This invention is particularly relevant to high speed optical communications switching, as in diverting a signal from one optical fiber to another. Several ferroelectric crystals, such as lithium niobate, potassium tantalate niobate, lithium tantalate, strontium barium niobate, and barium titanate, are photorefractive. Barium titanate has an unusually large electro-optic coefficient which has been effectively used to attain large nonlinear gain in two and four wave mixing configurations for beam coupling and optical phase configuration. The direction of nonlinear optical gain in a ferroelectric crystal is parallel or antiparallel (dependent on dominant carrier mobilities) to its ferroelectric c crystal axis. A property of ferroelectrics is that the direction of the c crystal axis can be repeatedly reversed by an externally applyed electric field. The direction of the net spontaneous polarization of the ferroelectric crystal is the c axis.